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external source of 24 volts is going to be connected switch 1 should be placed in its off (down) position. This ensures that a failure of the connected 24 volt DC source won’t cause the Model 45 to automatically revert to pulling power from the intercom circuit.
Some additional details might be helpful. Be certain to allow only the connected intercom circuit to supply power (switch 1 on) if it’s fully able to do so. Trying to draw current from a circuit that’s not capable of supplying the needs of the Model 45 will typically result in greatly degraded intercom audio quality. This is because the Model 45’s power supply circuit will always attempt to draw the current it requires. If it’s able to do so a constant
In conclusion, the Model 45 can function very well using the intercom circuit as its power source. But this requires that the circuit can meet the voltage and current requirements.
Model 45 Provides 2-Wire Party-Line Power Source
Configuration DIP switch 2 is used to se- lect whether or not the Model 45 will serve as an intercom power source, providing DC power and 200 ohm terminations to the intercom interface. When switch 2 is
in its off (down) position the Model 45 will not serve as an intercom power source. This setting is appropriate when an exter- nal intercom power supply is providing power and terminations to the connected
Auto Null Button Operation
A pushbutton switch, located on the Model 45’s front panel, is used to activate the auto nulling functions. A configuration parameter allows selection of the button’s operation. The choices are dual auto null mode and independent auto null mode. When dual auto null mode is selected
a single “tap” (press and release) on the pushbutton switch initiates a routine that begins with channel 1’s auto null sequence, followed immediately by channel 2’s auto null sequence.
The independent auto null mode allows the auto null function to be initiated for each channel as desired. A single “tap” will start the auto null routine for channel 1; two “taps” will start the routine for channel 2.
When configuration DIP switch 3 is in its off (down) position the dual auto null mode is selected. This is provided spe- cifically for cases where the Model 45’s
Model 45 User Guide | Issue Preliminary 2, March 2009 |
Studio Technologies, Inc. | Page 17 |